Published French Patent Application No. 2,500,525 describes an off-shore oil production installation which includes a plurality of well heads, each of which is associated with a corresponding auxiliary module which includes moving members such as valves. One side of each of these auxiliary modules is connected to the well head and the other side is connected to a collector which leads to a central structure where all the collectors are brought together and where further specialized accessory modules are located. The auxiliary modules are removable to enable them to be lifted to the surface for maintenance and for repair. It is thus necessary to leave a degree of play both between each module and its associated well head, and also between each module and the said collector once the module has been disconnected from these two items. However, the internal conduit(s) along the collector must be continued right up to the well head without any step, groove bump, or constriction of the conduit in the vicinity of the connectors since tools have to be sent along the conduit(s). This implies that the connections must be end-to-end connections going right up to the ends of the parts to be connected. Taking this into account as well as the play which is required to enable the auxiliary module to be inserted and removed, it is necessary to find the end of the collector located outside the auxiliary module and to pull it inside the module thereby making it possible to make the connection on the other side of the auxiliary module to the well head. This happens because the conduits cannot be looped inside the modules to give them a degree of elasticity, since the modules are of relatively small size and the loops would have to be of large diameter to pass the tools. This means that the collectors have to be pulled, and also that the auxiliary module described in the above-mentioned patent application includes a cradle which is movable sideways and which itself includes a length of conduit to be connected at one end to the collector and at the other end to the well head. Nonetheless, there reamains a difficulty in that said collectors, particularly in the vicinity of their ends, may become more or less dug-in over the course of time, which can make disconnection impossible since, once a collector is buried, it is no longer certain that it will remain flexible enough for its end to be pushed away by moving said cradle sideways in order to leave the minimum play necessary for the module to be removed.
Preferred embodiments of the present invention mitigate this drawback.